{"files"=>["https://ndownloader.figshare.com/files/857796"], "description"=>"<p>Results for logistic regression of ego drug use behavior at Wave II (1 = used marijuana in past 30 days, 0 = did not use) on Wave I covariates is shown in first three columns. Results for ordinary least squares regression of number of times ego uses marijuana at Wave II on Wave I covariates is shown in second three columns. The results suggest that both drug use and non-use may spread, but the spread of use is significantly stronger.</p>", "links"=>[], "tags"=>["mental health/sleep disorders", "mental health/substance abuse", "pediatrics and child health/child and adolescent psychiatry", "public health and epidemiology/social and behavioral determinants of health"], "article_id"=>528256, "categories"=>["Cancer", "Mental Health", "Medicine"], "users"=>["Sara C. Mednick", "Nicholas A. Christakis", "James H. Fowler"], "doi"=>"https://dx.doi.org/10.1371/journal.pone.0009775.t002", "stats"=>{"downloads"=>0, "page_views"=>1, "likes"=>0}, "figshare_url"=>"https://figshare.com/articles/_Marijuana_use_and_social_contacts_/528256", "title"=>"Marijuana use and social contacts.", "pos_in_sequence"=>0, "defined_type"=>3, "published_date"=>"2010-03-19 02:17:36"}

{"files"=>["https://ndownloader.figshare.com/files/857481"], "description"=>"<p><a href=\"http://www.plosone.org/article/info:doi/10.1371/journal.pone.0009775#pone-0009775-g001\" target=\"_blank\">Figure 1</a> is a network graph of the largest component of friends in Wave I of the Add Health study (year 1995), from a single school. Each node represents a subject (there are 800 shown) and its shape denotes gender (circles are female, squares are male). Lines between nodes indicate relationships (arrows point from the naming friend to the named friend). Node colour denotes nightly sleep duration (red for 6 hours or less, orange for 7 hours, white for 8 hours or more) and node size indicates frequency of marijuana use (the smallest nodes do not use marijuana, the largest report using at least daily). The network suggests clustering of both sleep and drug use behavior, and as we show in the statistical analysis, some of the overlap in clustering may result from a causal effect of sleep on drug use. Node placement is based on the Kamada-Kawai algorithm (see <a href=\"http://www.plosone.org/article/info:doi/10.1371/journal.pone.0009775#pone.0009775.s001\" target=\"_blank\">Text S1</a>) <a href=\"http://www.plosone.org/article/info:doi/10.1371/journal.pone.0009775#pone.0009775-Kamada1\" target=\"_blank\">[50]</a>.</p>", "links"=>[], "tags"=>["mental health/sleep disorders", "mental health/substance abuse", "pediatrics and child health/child and adolescent psychiatry", "public health and epidemiology/social and behavioral determinants of health"], "article_id"=>527939, "categories"=>["Cancer", "Mental Health", "Medicine"], "users"=>["Sara C. Mednick", "Nicholas A. Christakis", "James H. Fowler"], "doi"=>"https://dx.doi.org/10.1371/journal.pone.0009775.g001", "stats"=>{"downloads"=>2, "page_views"=>5, "likes"=>0}, "figshare_url"=>"https://figshare.com/articles/_Network_graph_/527939", "title"=>"Network graph.", "pos_in_sequence"=>0, "defined_type"=>1, "published_date"=>"2010-03-19 02:12:19"}

{"files"=>["https://ndownloader.figshare.com/files/857824"], "description"=>"<p><a href=\"http://www.plosone.org/article/info:doi/10.1371/journal.pone.0009775#pone-0009775-t003\" target=\"_blank\">Table 3</a> shows mediation effect of sleep on drug use. First three columns show logistic regression model of ego's marijuana use behavior (the outcome variable) on alter's sleep behavior (the explanatory variable). Second three columns show logistic regression model of ego's sleep behavior (the mediator variable) on alter's sleep behavior (the explanatory variable). Last three columns show logistic regression model of ego's marijuana use behavior (the outcome variable) on ego's sleep behavior (the mediator variable) controlling for alter's sleep behavior (the explanatory variable). Models were estimated using a general estimating equation with clustering on the ego and an independent working covariance structure. Models with an exchangeable correlation structure yielded poorer fit. Fit statistics show sum of squared deviance between predicted and observed values for the model and a null model with no covariates. A bootstrap procedure that takes into account uncertainty of both the effect of the independent variable on the mediator and the mediator on the outcome variable shows that when an alter starts sleeping ≤7 hours, it increases the likelihood of ego drug use by 4% (95% C.I. 1% to 7%) via its effect on the mediator (ego sleep), which represents approximately 20% of the total effect of alter sleep on ego drug use.</p>", "links"=>[], "tags"=>["mediates"], "article_id"=>528283, "categories"=>["Cancer", "Mental Health", "Medicine"], "users"=>["Sara C. Mednick", "Nicholas A. Christakis", "James H. Fowler"], "doi"=>"https://dx.doi.org/10.1371/journal.pone.0009775.t003", "stats"=>{"downloads"=>1, "page_views"=>4, "likes"=>0}, "figshare_url"=>"https://figshare.com/articles/_Ego_sleep_mediates_relationship_between_alter_sleep_and_ego_drug_use_/528283", "title"=>"Ego sleep mediates relationship between alter sleep and ego drug use.", "pos_in_sequence"=>0, "defined_type"=>3, "published_date"=>"2010-03-19 02:18:03"}

{"files"=>["https://ndownloader.figshare.com/files/426383"], "description"=>"<div><p>Troubled sleep is a commonly cited consequence of adolescent drug use, but it has rarely been studied as a cause. Nor have there been any studies of the extent to which sleep behavior can spread in social networks from person to person to person. Here we map the social networks of 8,349 adolescents in order to study how sleep behavior spreads, how drug use behavior spreads, and how a friend's sleep behavior influences one's own drug use. We find clusters of poor sleep behavior and drug use that extend up to four degrees of separation (to one's friends' friends' friends' friends) in the social network. Prospective regression models show that being central in the network negatively influences future sleep outcomes, but not vice versa. Moreover, if a friend sleeps ≤7 hours, it increases the likelihood a person sleeps ≤7 hours by 11%. If a friend uses marijuana, it increases the likelihood of marijuana use by 110%. Finally, the likelihood that an individual uses drugs increases by 19% when a friend sleeps ≤7 hours, and a mediation analysis shows that 20% of this effect results from the spread of sleep behavior from one person to another. This is the first study to suggest that the spread of one behavior in social networks influences the spread of another. The results indicate that interventions should focus on healthy sleep to prevent drug use and targeting specific individuals may improve outcomes across the entire social network.</p></div>", "links"=>[], "tags"=>["influences", "networks"], "article_id"=>144170, "categories"=>["Cancer", "Mental Health", "Medicine"], "users"=>["Sara C. Mednick", "Nicholas A. Christakis", "James H. Fowler"], "doi"=>"https://dx.doi.org/10.1371/journal.pone.0009775", "stats"=>{"downloads"=>3, "page_views"=>44, "likes"=>0}, "figshare_url"=>"https://figshare.com/articles/The_Spread_of_Sleep_Loss_Influences_Drug_Use_in_Adolescent_Social_Networks/144170", "title"=>"The Spread of Sleep Loss Influences Drug Use in Adolescent Social Networks", "pos_in_sequence"=>0, "defined_type"=>3, "published_date"=>"2010-03-19 01:09:30"}

{"files"=>["https://ndownloader.figshare.com/files/857579"], "description"=>"<p><a href=\"http://www.plosone.org/article/info:doi/10.1371/journal.pone.0009775#pone-0009775-g002\" target=\"_blank\">Figure 2</a> shows that the association between ego and alter sleep is significant up to four degrees of separation in both Wave I and Wave II. The left panel shows the percentage increase in the likelihood a person sleeps ≤7 hours if a friend at a certain social distance sleeps ≤7 hours. The right panel shows the percentage increase in the likelihood a person uses marijuana if a friend at a certain social distance uses marijuana. The relationship is strongest between individuals who are directly connected, but it remains significantly greater than zero at social distances up to 4 degrees of separation in both Wave I and Wave II. Thus, a person's sleep and drug use behavior is associated with the same behavior of other people up to 4 degrees removed from them in the network. Error bars are derived by comparing the conditional probability of the behavior in the observed network with an identical network in which topology and incidence of the behavior is preserved but the assignment of the behavior is randomly distributed [19,55 2008]. Alter social distance (degrees of separation) refers to closest social distance between the alter and ego (friend = distance 1, friend's friend = distance 2, <i>etc.</i>). Error bars show 95% confidence intervals.</p>", "links"=>[], "tags"=>["mental health/sleep disorders", "mental health/substance abuse", "pediatrics and child health/child and adolescent psychiatry", "public health and epidemiology/social and behavioral determinants of health"], "article_id"=>528036, "categories"=>["Cancer", "Mental Health", "Medicine"], "users"=>["Sara C. Mednick", "Nicholas A. Christakis", "James H. Fowler"], "doi"=>"https://dx.doi.org/10.1371/journal.pone.0009775.g002", "stats"=>{"downloads"=>1, "page_views"=>2, "likes"=>0}, "figshare_url"=>"https://figshare.com/articles/_Spread_of_sleep_and_drug_use_/528036", "title"=>"Spread of sleep and drug use.", "pos_in_sequence"=>0, "defined_type"=>1, "published_date"=>"2010-03-19 02:13:56"}